Syntheses, Structures, and Properties of Trinuclear Complexes [M(bpca)₂{M‘(hfac)₂}₂], Constructed with the Complexed Bridging Ligand [M(bpca)₂] [M, M‘ = Ni(II), Mn(II); Cu(II), Mn(II); Fe(II), Mn(II); Ni(II), Fe(II); and Fe(II), Fe(II); Hbpca = Bis(2-pyridylcarbonyl)amine, Hhfac = Hexafluoroacetylacetone]

Abstract

Five trinuclear complexes [M(bpca)(2)(M'(hfac)(2))(2)] (where MM'(2) = NiMn(2), CuMn(2), FeMn(2), NiFe(2), and FeFe(2); Hbpca = bis(2-pyridylcarbonyl)amine; and Hhfac = hexafluoroacetylacetone) were synthesized almost quantitatively by the reaction of [M(bpca)(2)] and [M'(hfac)(2)] in 1:2 molar ratio, and their structures and magnetic properties were investigated. Three complexes, with M' = Mn, crystallize in the same space group, Pna2(1), whereas two complexes, with M' = Fe, crystallize in P4(1), and complexes within each set are isostructural to one another. In all complexes, [M(bpca)(2)] acts as a bis-bidentate bridging ligand to form a linear trinuclear complex in which three metal ions are arranged in the manner M'-M-M'. The central metal ion is in a strong ligand field created by the N(6) donor set, and hence the Fe(II) in the [Fe(bpca)(2)] moiety is in a low-spin state. The terminal metal ions (M') are surrounded by O(6) donor sets with a moderate ligand field, which leads to the high-spin configuration of Fe(II). Three metal ions in all complexes are almost collinear, and metal-metal distances are ca. 5.5 A. The magnetic behavior of NiMn(2) and NiFe(2) shows a weak ferromagnetic interaction between the central Ni(II) ion and the terminal Mn(II) or Fe(II) ions. In these complexes, sigma-spin orbitals of the central Ni(II) ion and those of terminal metal ions have different symmetry about a 2-fold rotation axis through the Ni-N(amide)-M'(terminal) atoms, and this results in orthogonality between the neighboring sigma-spin orbitals and thus ferromagnetic interactions.

Structure and Magnetic Properties of a Trinuclear Nickel(II) Complex Constructed by bpca– Anions

“…Moreover, the value agrees well with the long intermetallic distances through the bpca – group in a κ 2 O:κ 3 N mode [Ni1 ··· Ni2 = 5.3018(4) and Ni2 ··· Ni3 = 5.3047(4) Å]. It is well‐known that the bpca – ligand is a good selection to tuning the orthogonality of spin orbitals and this merit could be documented by the compounds reported before 21. In this sense, the orthogonality of spin orbitals could be applied to analyze the antiferromagnetic behavior in complex 1 .…”

“…At the same time, orthogonality of spin orbitals from adjacent metal ions might play an important role in determining the magnetic interactions between metal ions 19,20. Up to now, the bpca – anion has been used to construct many hetero or homo metallic complexes 21–24. We recently reported one dinuclear Cu II cluster constructed by a bpca – anion 25.…”

Effects of 3d–4f Magnetic Exchange Interactions on the Dynamics of the Magnetization of DyIII‐MII‐DyIII Trinuclear Clusters

“…The bis(2‐pyridylcarbonyl)amine anion (bpca − ) is known for forming mononuclear complexes [M(bpca) 2 ] n + with divalent and trivalent metallic ions ( n =0, M II =Mn II ,17 Fe II ,18 CuII,19 Zn II 19 and RhII;20 n =1, M III =Fe III 18 and Rh III 20–22). In a next step, these complexes have allowed the obtainment of variable‐dimensional materials with interesting magnetic properties: homo and heterotrimetallic complexes,23, 24 one‐dimensional compounds with single chain magnet behavior,25 and two‐dimensional networks 26. All the previous mentioned compounds show that the bpca − ligand is rather efficient in transmitting the magnetic exchange interaction between 3d ions, while little is known for 4f ions.…”

Transition Metal Ion Directed Self‐Assembly of Polynuclear Coordination Complexes: Structural Characterization and Magnetic Properties

“…For the preparation of such architectures, well‐designed organic ligands with the appropriate choice of donors and bridging groups have become the focus of a great deal of research work. It is well‐known that polypyridyl groups have been very useful as programmed components in self‐assembly processes,21 and many poly‐pyridyl ligands have been proved to be very useful in the construction of polynuclear complexes. For example, the alkoxy‐diazine ligands have produced a series of highnuclearity complexes;5 the pendent‐arm ligand 1,4,7‐tris(acetophenoneoxime)‐1,4,7‐triazacyclononane has resulted in the formation of Cu II , Co II,III , Ni 4 II , and Mn 3 II,III complexes;22 the bis‐chelating ligand 1,2‐bis(2,2′‐bipyridine‐6‐yl)ethane has afforded a number of Mn complexes 18.…”